System Definition Document - Angelfire · Web viewSystem Definition Document Version 1.0 Revision...

SENG 6837

WAAS-NIES SimulatorSystem Definition Document

Version 1.0

WAAS-NIES Project Version: 1.0System Definition Document Date: 4/06/06

Revision HistoryDate Version Description Author

04/06/06 1.0 Draft Clay Bailey

Kalyn Bullock

Hanzela Hye

Tope Usanga

SENG 6837 Page 1 of 22


Table of Contents1. Introduction 4

1.1 Purpose 41.2 Scope 41.3 Definitions and Acronyms 4

1.3.1 Definitions 41.3.2 Acronyms and Abbreviations 4

1.4 References 41.5 Overview 5

2. System Overview 52.1 System Description 52.2 System Goals and Objectives 52.3 Driving Factors 6

3. Software Architecture Overview 7

4. Use Case View 84.1 Use Case Realization – Initialize and Start Simulation 14.2 Use Case Realization – WRS Retrieves Signal from Satellite (Input File) 24.3 Use Case Realization – Gather data from multiple WRSs into WMS 3

5. Process View 45.1 WAAS-NIES Initialization 45.2 WAAS-NIES Software Commanding 65.3 Simulator Software Update 8

6. Deployment View 9

7. Deployment View 10

8. External Interfaces 118.1 Inputs from other systems 118.2 Outputs to other systems 11

9. Operating and Design Constraints 129.1 Operating Constraints 129.2 Design Constraints 12



Table of FiguresFigure 2.1-1 WAAS High Level Concept.......................................................................................................................5Figure 3-1 High Level Software Deployment View.......................................................................................................7Figure 4.1-1 Initialize WAAS Use Case Diagram..........................................................................................................9Figure 4.2-1 Command Simulation Use Case Diagram................................................................................................10Figure 4.3-1 Update Software Use Case Diagram........................................................................................................11Figure 5.1-1 Activity Diagram for WAAS Initialization..............................................................................................12Figure 5.2-1 WAAS NIES Commanding Activity Diagram........................................................................................13Figure 5.3-1 WAAS Software Update Activity Diagram.............................................................................................14Figure 7-1 WAAS Deployment View...........................................................................................................................15Figure A-1 WAAS Architecture Option 1....................................................................................................................19Figure A-2 WAAS Architecture Option 2....................................................................................................................20



System Definition Document

1. Introduction

1.1 Purpose

The purpose of this system definition document is to capture the essential elements of the Wide Area Augmentation System Navigation Infrastructure Environment Simulator (WAAS-NIES), their relationships, characteristics, and behavior. It communicates the architectural decisions concerning the major hardware and software components of the WAAS-NIES. This document will drive the requirements definition, and will influence and constrain all subsequent activities including the hardware and software design, implementation, integration, and testing.

1.2 Scope

This system definition document defines the architecture of the WAAS-NIES and the WAAS-NIES support environment. It defines major software and hardware elements that are essential to satisfying the concept of operations for the system.

1.3 Definitions and Acronyms

1.3.1 DefinitionsEnvironment Simulator – The simulated ‘world’ in which the WAAS-NIES exists, and from which the WAAS-NIES receives commands

1.3.2 Acronyms and Abbreviations

CPU Central processing UnitCONOPS Concept of OperationsCOTS Commercial-off-the-ShelfGB gigabyteHz hertzPC Personal computerSDD System Definition DocumentTBD To be determinedTBS To be suppliedWAAS-NIES Wide Area Augmentation System Navigation Infrastructure Environment Simulator

1.4 ReferencesThe documents in the following table are considered a part of this document to the extent referenced within this document.

Document Number TitleConcept of Operations for the Wide Area Augmentation System Navigation Infrastructure Environment Simulator

1.5 OverviewThis first delivery of the System Definition Document (SDD) is provided prior to the release of the System Requirements Document (SRD). The SDD will be refined through the development of the WAAS-NIES Project. Section 2 provides an overview of the WAAS-NIES system. Section 3 provides the software architecture overview. Section 4 presents the major use cases for the system. Section 5 presents the process view of the system. Section 6 presents the deployment view of the system. External interfaces to the WAAS-NIES are presented in section 7, and constraints on the development of the design are presented in section 8.



2. System Overview

2.1 System DescriptionThe Wide Area Augmentation System (WAAS) is a GPS-based navigation and landing system that provides precision guidance to aircrafts at thousands of airports and airstrips, where there is currently no precision landing capability. WRS’s and integrity monitors are widely dispersed data collection sites that contain GPS/WAAS ranging receivers that monitor all signals from the GPS, as well as the WAAS geostationary satellites. The reference stations collect measurements from the GPS and WAAS satellites so that differential corrections, ionospheric delay information, GPS/WAAS accuracy, WAAS network time, GPS time, and UTC can be determined. The WRS and integrity monitor data are forwarded to the central data processing sites. These sites process the data in order to determine differential corrections, ionospheric delay information, and GPS/WAAS accuracy, as well as verify residual error bounds for each monitored satellite. The WAAS-NIES provides a simulation of the accuracy of the WAAS system that monitors GPS constellation of satellites. The WAAS-NIES subsystem hardware is scalable to meet requirements for simulating the WAAS system. The software of the WAAS-NIES subsystem is portable to other platforms (such as a PC) to allow re-use in smaller-scale simulations for single-task use.

Figure 2.1-1 WAAS-NIES High Level Concept

2.2 System Goals and ObjectivesThe goals and objectives of the WAAS-NIES are:

To provide an accurate simulation of the operation of calculating the delta error in a WAAS system To aid in the precision guidance of shuttle spacecraft to have a precise landing. To provide enough capacity for simulation of twenty five separate WRS stations. To allow users to control the delta error calculations through input from the Environment Simulator To provide the framework for future use to simulate a WAAS system to determine accurate calculations for

landing for shuttle spacecrafts

2.3 Driving FactorsDriving factors for the selection of the system architecture include the following:

The visual model complexity combined with the number of WRS stations available at one time drives the need for the simulator to operate at 70% of the processor, memory, and input/output capability.

The future use of the system for modeling GPS-based navigation and landing system that provides



precision guidance for shuttle space crafts is a higher need to the return to flight missions and for the government agency continue exploration.

Custom reporting of various input files will provide a more realistic visual model of complex signals in space

o Allows more detail to more easily confirm landing situations.o Drives the architecture requirements to programmable graphics processing units

Graphics processor capabilities are improving at a remarkably high rate. New technology has made it possible to perform high bandwidth graphics processing with personal computer (PC) and network architectures that just a year ago could only be performed on high-end dedicated commercial off the shelf (COTS) graphics systems with proprietary architectures. Conversely, the high rate of change in the industry will drive the industry to abandon current architectures that could be marginally acceptable for the application, but unsupportable in the near future (within 3-5 years). Higher-end COTS graphics proprietary solutions are also changing, but would likely be supported in the future at significantly high costs.

3. Software Architecture OverviewA high-level illustration of the WAAS-NIES software architecture is shown in figure 4-1. The Environment Simulator contains functional models for the simulated “universe” and provides the user interface to itself and to the WAAS-NIES. The Environment Simulator maintains control of all objects in the simulated universe and state information for all objects in the simulated universe with respect to an inertial coordinate system (known as the inertial state vector). The WAAS-NIES simulator interfaces to the Environment Simulator to receive commands and to receive the inertial state vectors related to the objects in the universe.

Figure 3-1 High Level Software Deployment View



4. Use Case View Figure 4-1 illustrates how the WAAS-NIES system use cases are distributed. The User initializes the simulator and starts the simulator software. Once the user initializes the settings used, the simulator may be started. Further detail for the WAAS-NIES initialization, receiving signals, gathering and processing the signals, calculating the delta error, and creating an output message are provided in sections 4.1 through 4.3.

Figure 4-1 System Level Use Case



4.1 Use Case Realization – Initialize and Start Simulation

Figure 4.1-1 Initialize WAAS Use Case Diagram

Actions for this use case are:

Use Case Actor ActionUser loads Simulator Software

The user runs the executable (in Matlab) and functions and variables are initialized.

User Provides location for input files

The user verifies or changes the location of the input files being used in simulation.

User provides location for output file.

The user verifies or changes the location of the output files used in simulation.

User starts the simulation

The user clicks on a button to start the simulation.



4.2 Use Case Realization – WRS Retrieves Signal from Satellite (Input File)

Figure 4.2-1 WRS retrieves signal from satellite Use Case Diagram


Use Case Actor ActionSimulator retrieves signal data (coordinates) from input files in WRSs

The signal data provided by the user is retrieved.

Simulator Environment alters signal (coordinates)

The environment simulator provides error simulation to the signal retrieved in the previous step. The original signal is “altered” and outputs a signal with errors.

Simulator saves data collected from Environment to output file

The data points collected from the previous step is saved to an output file.



4.3 Use Case Realization – Gather data from multiple WRSs into WMS

Figure 4.3-1 Gather data from multiple WRS into WMS Use Case Diagram


Simulator gets WRS location data for each WRS from Input file2.

The location of the 25 WRS sites is retrieved from a data file.

Simulator saves the data for each WRS in output file

The WRS location along with the signal received is collected and stored.

Get current satellite position

The predetermined satellite positions.

Simulator gathers WRS data and satellite position into single WMS module

After all the WRS data and satellite position have been collected, they are sent to the WMS module.



4.4 Calculate Delta Error in Data

Figure 4.4-1 Calculate Delta Error Use Case Diagram



4.4.1 Calculate Line of Sight and IPP

Figure 4.4.1-1 Activity diagram for the Calculate Line of Sight and IPP Use Case


Compute Line of Sight Location data of reference stations and satellites are used to compute Line Of Sight (LOS) vectors in ECEF coordinates.

Translate LOS into east-north-up coordinates.

The Earth Centered, Earth Focused (ECEF) coordinates are translated into east-north-up coordinates.

Calculate elevation angle

Elevation angle is calculated.

Compute Ionosphere Pierce Points

The locations of the Ionosphere Pierce Points (IPP) are computed.



4.4.2 Calculate Troposphere and CNMP Errors

Figure 4.4.1-1 Activity diagram for the Calculate Troposphere and CNMP Errors Use Case

Actions for this use case:

Generate Troposphere correction mapping function

The troposphere sub-module takes elevation angles as input and generates troposphere correction mapping function for satellite elevation.

Calculate Troposphere error

The troposphere correction mapping function is used to calculate the troposphere error.

Calculate CNMP noise floor

The Code Noise and Multi Path (CNMP) sub-module calculates the CNMP noise floor of the satellite frequencies.

Compute CNMP error The CNMP error is computed using the elevation angle and the noise floor calculation.



4.4.3 Calculate UDRE and GIVE Errors

Figure 4.4.1-1 Activity diagram for the Calculate Troposphere and CNMP Errors Use Case


Pass troposphere and CNMP error to UDRE

The troposphere and CNMP error variances are fed into the UDRE module

Compute UDRE The User Defined Range Error (UDRE) is computed using the ionosphere and CNMP errors, and line-of sight.

Get IPPs The IPPs are retrieved from the from use case 4.4.1Compute GIVE The Grid Ionosphere Vertical Error (GIVE) is computed using the IPPs and

Ionosphere and CNMP error information.

5. Process View The process view consists of activity diagrams for the WAAS-NIES Initialization, WAAS-NIES Software Commanding, and WAAS-NIES Software Update.



5.1 WAAS-NIES InitializationWAAS-NIES Initialization is illustrated in figure 5.1-1. The User initializes the WRS-Environment Simulator and is prompted to select a software version. The user selects the software version and the WRS-Environment Simulator displays the proper version from the WRS Network. The WRS-Environment Simulator generates an ongoing status report for the user. The User commands the Environment simulator to initialize the software. The Environment Simulator then queries whether the proper version of the software is loaded. If it is, the WRS-Environment Simulator initializes the software to begin.. If not, the WRS-Environment Simulator retrieves the proper software version from the WRS Network and confirms that it has the proper version in conjunction with the WRS-Environment Simulator, and the WRS-Environment Simulator proceeds to initialize the software. The software enters the ready state after initialization and sends status to the WRS Station. The WRS-Environment Simulator reports the initialization for command status to the WRS-workstation user.



Figure 5.1-1 Activity Diagram for WAAS-NIES Simulation Initialization


User

Initialize WRS-Workstation

SW Version Detected

Command Initialize Software

Command Input

Generate WRS Report

Initialized

Prompt for SW Version

Retrieve SW version

Initialize Software

Green Status

Check to Ensure SW Version is

correct

Simulator Initialized

Initialized

Report SW Version

WRS-Environment Simulator

WRS Network Simulator

Start

Confirmation Status

Ready Status

Send Ready Status


5.2 WAAS-NIES Software CommandingFigure 5.2-1 illustrates the software command commanding activity. The User commands the Simulator through the WRS-Environment Simulator interface. The Software enters the “on” state and returns the “on” flag to the Environment Simulator. The Environment Simulator sends state data to the Simulator continuously after the start of the software. The user commands the control panel of the WAAS-NIES to start inputting files through the Environment Simulator interface. The Simulator then uses the state data to generate the input status for the WRS shuttle. The Simulator sends the image to the WRS Workstation, where the User can view the generated report. The User may command the software to generate the delta error, variance, or projected results via the WRS-Environment Simulator user interface. The Environment Simulator sends the new state data information through the simulator. The Software repeats the report generation process and sends the updated report to the WRS Display Monitor, where the new report can be viewed by the User.



Figure 5.2-1 WAAS-NIES SoftwareCommanding Activity Diagram


User

Command Prompt for Simulator

Command Input File

View Results

Issue Simulator Command

Delta Error

Variance

Projection

Print/View Output Report

Simulator Command-On

Send Data

Input Received

Send State Change

Simulator Status

Generate Output

Send Output

Green Status

Input Reception Status

Display Status

Display Output

WRS-Environment Simulator

Software Display Monitor

Start


5.3 Simulator Software UpdateThe WAAS-NIES software update activity is illustrated in Figure 5.3-1. This activity applies to WRS Network Database updates as well as software updates. The Developer updates Simulation software on the Development System. The Developer then issues the command to save the updated software. The Development System saves the software to the WRS-Network Storage. The WRS-Network Storage enters the ready “status” for access by the WRS-Environment Simulator or Network.

Figure 5.3-1 WAAS-NIES Software Update Activity Diagram


Programmer

no

Update Simulator Software

Save Simulator Software

Ready Status

Simulator Portion Updates

Write to WRS-Network

Simulator SW Saved

Development System WRS-Network

Start

Ensure Ready Status

yes


6. Deployment View The Deployment View illustrates the distribution of major software functions to the hardware. The WAAS-NIES Development System contains all software required to build the Simulator software and visual modes that illustrate connectivity. It contains the source for the software and tools for development. The WAAS-NIES Simulator Processor contains the visual models and the software for generating status and reports. It also contains the Environment Simulator interface for returning the status and reports to the WRS-Network. The WRS-Network stores the Simulation Data and Environment Simulator software. The Environment Simulator contains the WRS-Database. It contains the user interface for Simulator commanding and will contain the software for status, regarding the display panel for future projections.


Development Platform

Open-Source Tools/Code

Matlab Execution

Development System

Network Storage Space

WRS-Network

Simulator Command Handling

Signal Error

Status Report/Output Generation

WAAS-NIES Simulator ProcessorDocumentation- Processor Speed=2.7Ghz or higherMemory: 4 Gigs or higherGraphic Cards: 2OS=Linux/WindowsApplication 1 = MAtlab CodeApplication 2 = C++

Input ReceptionSimulator EfficiencyDelta Error CalculationVarianceIllustration/Display

WAAS-NIES Panel DisplayDocumentation- Digital Display with high refresh rate. Capability of providing results in graph/tabularized format.

1 GB Ethernet/T1

1 GB

1 GB T1

1 GB


Figure 7-1 WAAS-NIESS Deployment View



7. External Interface

7.1 Inputs from other systemsThe WAAS simulator receives signals from the satellite through the WAAS Reference Station. It also creates error information that will be used to detect the delta error of the signal.

7.2 Outputs to other systemsThe simulator outputs the augmentation message to the GEO satellite.



8. Operating and Design Constraints

8.1 Operating ConstraintsThe WAAS is dependent upon receiving a signal from a satellite in space. The signal is received at one of many simulated WRS sites. The simulator needs to have multiple WRS sites; each one able to detect errors in signals using their location.

8.2 Design ConstraintsThe following design constraints have been defined:

The WAAS must be capable of capturing a graphical representation for the user. The WAAS must be designed for 150% expandability. The WAAS must be designed to operate at 70% of the processor, memory, and input/output capability. The WAAS must be designed to send GPS information to simulated spacecrafts with accuracy of ??

meters. The WAAS must be designed to detect and report collisions between two designated paths of signals. The WAAS must be capable of receiving multiple reports, simultaneously, while scanning.


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